Refining silicon-containing iron-chromium alloys



Patented Aug. 24, 1926.

BYRAMJI SAKLATWALLA. OECRAFTON, PENNSYLVANIA.

EEFINING SILICON-CONTAINING IRON-GHROMIUM ALLOYS.

No Drawing.

The present invention. relates to refining silicon-containing and particularly such alloys in which the silicon is Without substantial oxidation of.

iron-chromium to a process for refining alloys,

oxidizable the chromium. The invention is particularly applicable to the refinlng of high silicon ferrochromium and will be described ticular reference to it,

with parit being understood however that the process may be used for the refining of other silicon-containing ironchromium alloys, such for example as chrome steels or irons. alloy, which is high The ferro-chromium 1n silicon, s smelted with an oxidizing agent which oxidizes the silicon without substantially oxidizing the chromium. have used calcium carbonate. carbonate upon heating y1elds As suchan oxidizing agent,

The calcium carbon (boxide which, in turn, yields a part of its oxygen to oxidize the silicon. carbonate is preferably mixed wt The calcium th calcium oxide which apparently serves as a diluent and which. together with the calcium oxide produced from the calcium carbonate by the liberation of its carbon dioxide,

combines with the silica formed by the oxidation of the silicon. It is found that when the hi gh silicon calcium carbonate and calcium ferro-chromium is smelted with the oxide. the

silicon canbe oxidized without any appreciable oxidation of the chromium.

The mixture of calcium carbonate and calcium oxide may be used alone,

but it is found that the silicon content can be reduced to a greater extent, say under 5 of one per cent for special purposes, quantity of potassium or sodium chrome or iron ore, the calcium carbonate mixture;

by the addition of a small nitrate. or

or a mixture of them. to and calcium oxide The activlty of the oxidizing reaction can be controlled by reguh-iting the current density and voltage in the furnace.

Increasing the temperature by increasing the current density or voltage, increases the activity it is possible thus to oxidize the s of the reaction. I have found that ilicon content without any appreciable sacrifice of the chromium content.

Slight additions ing facilitate the refining.

of fluorspar to the oxidizmixture are 1n some cases desirable to Typical examples of the oxidizing mixture are:

200 lbs. calcium carbonate, 30

0 lbs. cal- Applieation filed March 11, 1922. Serial No. 548,085.

cium oxide, 50 lbs. chrome ore, 50 lbs. iron ore. 50' lbs. fluorspar, or

200 lbs. calcium carbonate, 300 lbs. calcium oxide, 100 lbs. sodium nitrate. or

200 lbs. calcium carbonate, 300 lbs. calcium'oxide, 50 lbs. chrome ore, 50 lbs. sodium nitrate, 50 lbs. fluorspar.

As an example of the composition of the refined alloy, may be cited:

Alloy previous to refining:

Per cent. Cr 39.46 Si 34.4 C 0.22

Alloy after refining:

Per cent. Cru 65.80 Si 0.03 C 0.16

Another example is as follows: Alloy previous to refining:

' Per cent. Cr 5.61 Si 26.8 C 0.59

Alloy after refining:

Percent. Cr. 63.70 Si i 9.03 C 0.34

The oxidizingmixture is added to the high silicon ferro-chromium, which is in the molten state. The oxidizing mixture is preferably added in successive installments until an analysis of a sample shows thatthe silicon content of the alloy has been reduced to the desired percentage.

While I have specifically described the preferred wayof carrying out my process, his to be understood that the invention is not limited to the described details, but may be otherwise embodied within the scope of the following claims.

I claim l 1. The process of refining silicon-containing iron-chromium alloys, which consists in smelting the alloy with a mixture containing calcium carbonate, calcium oxide and a small amount of a nitrate, substantially as described.

2. The process of refining silicon-contaim ing iron-chromium alloys, which consists in smelting the alloy with a mixture containing calcium carbonate, calcium oxide, and

asmall quantity of a nitrate and chrome or ironore, substantially as described.

3. The process of refining high silicon iron-chromium alloys, which comprises treating the alloyin the molten state with calcium oxide and calcium carbonate in an amount sufiicient to. act as an oxidizing ,agent, substantiallyas described.

4. The process of refining high silicon iron-chromium alloys, which comprises treating the alloy in the molten state with calcium oxide, chromium or iron oxide, and calcium carbonate in'an amount sufficient to act as an oxidizing: agent, substantially as described.

treating the alloy in the molten state with a carbonate decomposable at furnace temperatures in an amount sufiicient to act as an comprises oxidizing agent, substantially as described.

6. The process of refining high vsilicon iron-chromium alloys, which comprises subjecting the allo) in amolten state to the oxidizing action of calcium carbonate, substantially as described.

In testimony whereof I have hereunto set my hand.

BYRAMJI' D. SAKLATWALLA; 

